The housing of an electronic device, particularly of a mobile communication device, must resist vibrations and impacts and exhibit a shielding effect against external, electromagnetic wave energy disturbances as well as internal, electromagnetic energy. Further, the housing of an electronic device containing a heat-generating component must radiate the generated heat efficiently. Although not heretofore known, it is also desirable for such a housing to insulate sensitive components from severe temperature variations. In case of a portable electronic device, its housing must also be small in size and weight. And the housing of an electronic device which is likely to be used in the rain, is required to be rainproof.
In the interior of the housing of a mobile communication device it has been considered necessary to support or fix modules into the housing with bolts or the like and to provide a partition to prevent electromagnetic interference between circuits.
FIGS. 18(a-d) show a prior art housing of such a mobile communication device. FIG. 18(a) is a plan view, FIG. 18(b) is a front view, FIG. 18(c) is a left side view, and FIG. 18(d) is a right side view of the prior art device. In FIGS. 18(a) to 18(d), the reference numeral 1 generally denotes a transceiver contained in an electronic device housing comprising a cover 101 and a case 107, the housing containing a radio apparatus and a logic controller. A coaxial connector 2 for the connection with an external antenna is attached to a side face of the transceiver housing.
The transceiver 1 is provided with a handset connector (not shown) which extends through a handset connector housing opening 3 for use together with a handset (also not shown). The transceiver is also provided with an external microphone connector (not shown) which extends through an external microphone housing opening 4 and a power cable connector (not shown) which extends through a power cable connector opening 5 for the supply of power from a vehicular battery. The transceiver case 107 is further provided with support legs 6a-6d at four corners of the bottom 107b thereof. Square recesses 7a-7d for mounting the case to a mounting bracket 8 are formed between the bottom 107b and the support legs 6a-6d.
A mounting bracket 8 is provided for mounting the transceiver 1 to a vehicle or the like. The mounting bracket 8 has pawls or tabs 9a-9d at four corners thereof provided so as to be fittably received in the square recesses 7a-7d provided on the case 107. The mounting bracket 8 is further provided with a release lever 10 at an end thereof. When the transceiver 1 is slid on the mounting bracket 8 until the pawls or tabs 9a-9d of the mounting bracket 8 are fitted in the square recesses 7a-7d of the case 107, a lock receptacle 11 on the bottom 107b of the transceiver case 107 and the front end of the release lever 10 come into engagement with each other to lock the transceiver 1 to the mounting bracket 8.
For removing (unlocking) the transceiver 1 from the mounting bracket 8, the release lever 10 is shifted laterally to disengage the front end of the release lever 10 from the lock receptacle 11 to effect unlocking. In the bottom of the mounting bracket 8 are formed mounting holes 8a-8d for fixing the bracket 8 to the body of a vehicle or the like with bolts fitted through the mounting holes 8a-8d.
Numeral 12 denotes a rail which is formed of nylon or the like to provide a relatively frictionless slidable engagement between the mounting bracket 8 and the transceiver for good slippage at the time of mounting of the transceiver 1. The rail 12 is attached to the mounting bracket 8 by press-fitting a concave portion of the channel shaped rail 12 onto the upper edge of a side plate 8sp of the bracket. The bottom of the housing 107 of the transceiver 1 is provided with a guide 13 arranged in engageable relationship with the rail 12 to facilitate the mounting and support of the transceiver 1 to the bracket 8.
FIG. 19 is an exploded perspective view of the conventional transceiver 1 shown in FIG. 18. In FIG. 19, the numeral 101 denotes a cover; number 102 denotes a conductive shield ring comprising, for example, a rubber ring with a metallic mesh disposed therearound; and numerals 103a to 103c denote a logic (LCU) module, a receiver/synthesizer module and a transmitter (TX) module, respectively.
On the receiver/synthesizer module 103b is mounted a TCXO (Temperature Compensated Crystal Oscillator) 104 which ensures frequency stability of the synthesizer, and the transmitter module 103c has a transmission power amplifier 105 and an isolator 106 mounted thereon.
Numeral 107 denotes the case, to which is attached the antenna connector 2 with a screw 2c through a water-proof rubber 2a and a metallic mounting piece 2b. Numeral 108 denotes an O-ring made of rubber for waterproofing.
Conventional examples related to the electronic device housing comprising the cover 101 and the case 107 are mentioned in Japanese Utility Model Laid-Open Nos. 164289/83, 164292/83, 23495/87 and 78798/87.
The cover 101 is formed by die casting of aluminum. Its surface has been subjected to a dewaxing treatment for removing oil and fat adhered thereto at the time of a secondary machining such as punching for the die cast, a coating treatment for preventing oxidation and an outer surface coating treatment for covering the texture of aluminum.
FIG. 20(a) is a view corresponding to both the section taken on line C--C of the cover 101 and the case 107; FIG. 20(b) is an enlarged sectional view illustrating the abutment between the cover 101 and the case 107; and FIG. 20(c) is an enlarged sectional view of an abutment between the logic module 103a and a projection 101c of the cover 101.
In FIGS. 20(a) to 20(c), a recess 101a for the shield ring 102 is formed in the peripheral edge of the cover 101 on the side in juxtaposition with the case 107. Like the cover 101, the case 107 is also formed by die casting of aluminum and the surface thereof has been subjected to the aforementioned treatments.
The portion of the case 107 opposed to the recess 101a is formed as a convex projection 107a. A recess 107b for the O-ring 108, which uses the convex 107a as part of the side wall thereof, is formed in the case 107. Therefore, when the cover 101 is attached to the case 107, the shield ring 102 fitted in the recess 101a of the cover 101 comes into contact with the convex 107a of the case 107, so the open portion of the case 107 is completely electromagnetically closed by the shield ring 102 and cover 101, resulting in the protection of the internal circuitry against external, electromagnetic wave energy disturbances. Undesired electromagnetic energy generated from the internal circuitry is also prevented from leaking to the exterior of the transceiver 1, thereby preventing disturbance to other electronic devices.
Likewise, the O-ring 108 fitted in the recess 107b of the case 107 comes into pressure contact with a convex 101b of the cover upon closing of the cover 101, so that the transceiver 1 is sealed hermetically. Consequently, even when the transceiver 1 is exposed to water drops such as rain, the drops are prevented from entering the interior, so the internal circuitry is protected.
In FIG. 19, the transmitter module 103c is mounted to a transmitter module receiving portion 107c of the case 107 using bolts, while the transmission power amplifier 105 and the isolator 106 are mounted to the case 107 directly or through a good heat conductor 109 (FIG. 20a).
The peripheral surface of the case 107 is formed with heat radiation fins 107g (FIG. 19) to radiate the heat generated from the transmission power amplifier 105, isolator 106, etc. during the operation of the transmitter. This is accomplished efficiently through use of the aluminum die-cast case 107 (a good heat conductor) and the heat radiation fins 107g. A shield plate (not shown) is provided over the transmitter module 103c and is attached to the case 107 to prevent electromagnetic interference with other circuit blocks.
The receiver/synthesizer module 103b is fixed to a base plate receiving portion 107d of the case, for example with bolts. The module is electromagnetically shielded by a partition 107e of the case 107 to prevent electromagnetic interference from the transmitter circuit from being received in the module receiving portion 107c. This shielding is accomplished by means of a partition 107e of the case 107. On the bottom of the case 107 is formed a low partition 107f which contacts the back of the receiver/synthesizer module 103b, thereby preventing electromagnetic interference between the receiver portion and the synthesizer portion.
Over the transmitter module 103c thus received in the case and the shield plate mounted thereover, the logic module 103a is attached to the case 107, with its component mounting side facing down. Attachment to the case 107 is made bolts for example securing it to the partition 107e. A multiple contact connector 110 is provided to allow opposed connection with another module, e.g. the receiver/synthesizer module 103b.
As shown in FIG. 20(c), the cover 101 is provided with the projection 101c which has a recess 101d, for abutment with the logic module 103a when the cover is attached to the case 107. A shield ring 102a is fitted in the recess 101d. Before the cover 101 is closed, the shield ring 102a is provided in the recess 101d. Upon closing of the cover, the shield ring 102a comes into contact with the logic module 103a and a rubbery core thereof is deflected and comes into pressure contact with the cover 101 and the logic module 103a, thus permitting electromagnetic shielding between circuits in the logic module 103a.
As described above, the conventional electronic device housing is formed of the aluminum die-cast cover and case, so in comparison with other conventional housings formed of a metal such as iron or brass, it is strong, highly resistant to external impacts and vibrations, exhibits a satisfactory heat radiation effect, and can be molded integrally as compared with a housing constituted by a combination of sheet metals, allowing formation of partitions in the inside of the housing to easily reduce electromagnetic interference between modules and also between intramodule circuits. Use of this material facilitates construction of a water resistant housing having electromagnetic shielding effects. Thus, such a housing exhibits excellent performance and functions.
However, although the aluminum material is lighter than many other metals, it is heavier than other diverse structural materials, and for integral molding, it is necessary that an injection molding be performed at high temperature and pressure by aluminum die casting. Therefore, it is difficult to adopt a complicated die structure, and in order to obtain a fine structure it is necessary to use a lot of dies, including side-core dies. The finer the structure, the easier the breakage of the die, and because of a high temperature and high pressure injection molding and hence a great temperature difference from ordinary temperature (room temperature), the die is apt to break after only a short service life.
Consequently, it is desirable to reduce the number of shots (the number of products capable of being produced from a single die), and since burr is formed on the aluminum die cast surface, it is absolutely necessary to perform a secondary machining such as forming a tapped hole for the removal of the burr. And because an oily machine is used for the secondary machining, a dewaxing treatment is required to remove the oil and fat adhered to the surface. To cover the metal texture of aluminum it is necessary to apply, for example, coating thereto.
Moreover, as compared with other diverse structural materials, aluminum is high in cost per unit volume and requires much time for the above secondary machining, surface treatment, etc., and there is a limit in the reduction of cost.
Perhaps even more importantly, although aluminum is metal and it is a good heat conductor, conducting the heat from heat-generating components to the exterior in a satisfactory manner, it also conducts external temperature variations to the interior of the housing. Further, aluminum cannot insulate sensitive components from normal temperature fluctuations and thus sensitive components must be designed for a greater operating temperature range. Additionally, the heat conducted from heat generating components in the housing to other components contained therein increases the temperature variations even further. Thus, additional heat is transmitted to, for example, the TCXO on the receiver/synthesizer module; and the TCXO must therefore have a design temperature range which is the working outside air temperature range plus the temperature rise caused by such transmission of the heat. This leads to increased cost as components capable of withstanding high temperatures are required or results in shortening the operating life of components.